Exception Handling

In Java, when an error occurs, it "throws" an Exception. We use a Try-Catch block to "catch" that exception and handle it gracefully without stopping the whole program.

The Keyword Quartet

1. try: Wrap the "dangerous" code that might fail here.

2. catch: If an error happens in the try block, the code jumps here. This is where you put your "Plan B."

3. finally: This block runs no matter what, even if there was no error. It's perfect for "cleaning up" (like closing a file).

4. throw: Used to manually create an error (e.g., "If age < 18, throw an error").

The Code Example:

public class ExceptionDemo {
    public static void main(String[] args) {
        int[] numbers = {10, 20, 30};

        try {
            System.out.println("Attempting to access the 10th element...");
            // This will fail because the array only has 3 items
            System.out.println(numbers[10]); 
            
            System.out.println("This line will never run!");
            
        } catch (ArrayIndexOutOfBoundsException e) {
            // Plan B: Handle the specific error
            System.out.println("ERROR: You tried to access an index that doesn't exist!");
            System.out.println("Message: " + e.getMessage());
            
        } catch (Exception e) {
            // General safety net for any other types of errors
            System.out.println("Something else went wrong.");
            
        } finally {
            // This always runs
            System.out.println("Cleanup: Execution of the try-catch block is finished.");
        }

        System.out.println("\nLook! The program is still running and didn't crash.");
    }
}

Expected output:

Attempting to access the 10th element...
ERROR: You tried to access an index that doesn't exist!
Message: Index 10 out of bounds for length 3
Cleanup: Execution of the try-catch block is finished.

Look! The program is still running and didn't crash.

Attempting to access the 10th element...

ERROR: You tried to access an index that doesn't exist!

Message: Index 10 out of bounds for length 3

Cleanup: Execution of the try-catch block is finished.

Look! The program is still running and didn't crash.